Graded finder system



Dec. 24, 1929. w. AITKEN 1,740,559

GRADED FINDER SYSTEM Original Filed May 21, 1925 2 Sheets-Sheet l A Fz9:l

D E M2 22am Fiflken Dec. 24, 1929. w; AITKEN 1,740,559

GRADED FINDER SYSTEM Original Filed May 21, 1925 2 Sheets-Sheet 2 Patented Dec. 24, 1929 UNITED STATES WILLIAM AITKEN, or LoNnoN, ENGLAND,

ASSIGNOR, BY MESNE ASSIGNMENTS, TO

AUTOMATIC ELECTRIC INC., OF CHICAGO, ILLINOIS, A CORPORATION OF DELA- WARE GRADED FINDER SYSTEM Application filed May 21, 1925, Serial No. 31,808, and in Great Britain August 21, 1924. Renewed September The present invention relates to telephone systems employing automatic switches and is more particularly concerned with systems employing switches of the backwardly hunting or finder type. As is well known, the function performed by these switches isessentially similar to that of line-switches of the forwardly hunting type, but the controlling arrangements must of course be dififerent and in general the quantities involved will be different also. When the switches are used for connecting a calling subscribers line with a first numerical switch, it line-switches are used, they must be provided individual to each calling line and hence a large number are required. These switches, however, are

comparatively cheap and simple to manufacture and further, the selector switches to which the line-switches have access may be arranged in comparatively large groups, for instance groups of 25, so that the number of expensive selector switches is reduced to a minimum. -With finderswitches on the other hand, if they are arranged to be of large capacity, a special switch construction is necessary if unduly long hunting time is to be avoided, while it they are standard switches of small capacity, not only must a much larger number be employed, but since each finder-switch is usually directly linked to a selector switch, the expensive selector switches must also be provided in greater quantity.

The object of the present invention is to overcome this drawback to the use of finderswitches and to enable a small type of finderswitch similar in construction to a line switch to be employed without unduly increasing the number of numerical switches to which the finder-switches are linked.

According to the invention, in a system employing finder-switches which hunt for lines arranged in groups corresponding to the capacity of each finder-switch, some of thefinder-switches are connected to individual terminals of the succeeding switching devices, while others are connected in multiple to the terminals of the succeeding switching device.

According to another feature of the invention, in a system employing backwardly hunting switches for connecting subscribers lines to numerical switches, the numerical switches are arranged to be taken into use in a definite order of priority, in which order the switches are accessible from successively larger groups of subscribers lines.

A further feature of the invention is that in a system employing finder switches for connecting a calling subscribers line to a first numerical switch, the finders are adapt ed to be taken into use in a definite order of priority, the finders adapted to be first taken into use for connecting with a calling line being linked to individual switching devices, while those taken into use when all of the first class are busy are connected in successively larger groups to switching devices common to more than one finder.

The invention will be better understood from the following description of a preferred embodiment taken in conjunction with the accompanying drawings. It will be understood that though the form described concerns the novel arrangements of finders for connecting subscribers lines to numerical switches, the invention is not limited to such use nor to the exact circuit arrangements shown.

Referring now to the drawings, Fig. 1 shows various arrangements of finders which are possible according to the invention; in illustrations A and B 2-5 point finders are used, and in illustration C 50 point finders are used. D and C respectively show two arrangements of what may be termed grading in the banks of the finder allotters associated with the various groups.

Fig. 2 is a circuitdiagram showing the actual connect-ions when finders of two difi'erent groups are connected in multiple to a common succeeding switch, while Fig.3 shows the wiring of the finder allotter banks.

In illustration A there are shown two groups of subscribers lines a and 6, each group comprising 25 lines which are served by five finder-switches. In each group it is arranged that by means of an allotter (not shown) the finder-switches are taken into use in a definite order of priority, for instance the trunk lines associated with the finders in LL at as that employed in grading as applied to forwardly hunting switches.

Illustration r3 shows a possible arrangement with three groups of subscribers lines- 0, (Z and c, with a somewhat heavier tratfic, so that each group is served by siX fincerswitches. in this case the first two trunks 8 and 9, l and l1, l2 and 13, for each group are individuals, the next two in each group, l t, and 18 are common to two groups, while the last two 16 and 17 are common to all three groups. By this arrangement a total of 11 trunks is made to serve for the three groups as against 18 if each group had all its'siX trunks individual.

In illustration C the numbers are slightly different, but the principle remains the same. In this case there are two groups of subscribers lines 7 and 9 and each comprises 50 lines. Underthesecircumstances 9 finders are provided to deal with the 'trafficof each group and the first five trunks 19%? and 2 1 223 are individual, and the last four 29432 are common, so that a total of i l suiiices.

The illustrations D and E sho in a difien ent manner the grouping arrangement.

.These illustrations represent the bank contacts of the finder allotters, one of which is associated with each group. In D it 15 sumed that there are tour groups and hence four allotters and that six finders are pro vided to take care of the trarlic in each group, and moreover that the home position of Ch allotter is at the bottom of each vertical row orl contacts. It will be seen then that the first two contacts are connected to individual finder links, the third and fourth contacts are connected to links which are common to two groups, though the grouping is differentin the two cases, while the fifth and sixth positions lead to finders which are common to all four groups. In illustration E, four groups a again assumed and seven finders, and in this case the connection of the finders in pairs is further mixed on the fourth contacts.

Fig. 2 shows detailed circuits for the case in which two finders are connected together to a common succeeding switch for instance a first selector. The circuits would not however need alteration if a larger number of finders-were employedin multiple, the connections of the additional switches being readily apparent to those versed the art. The finder switches. represented by F5 and F8 are. mechanicaHy identical lwith,flineswitches oi well known type, with ipers having no normal position and moving always in the same direction and having either or contacts. A suitable number of these switches are provided for each group of lines and the order in which these switches are taken into use is determined by a finder allotter such as FA. This switch is mechanicallyidentieal with any of the finders except that it is provided with a normal position to,- which it returns when not actually in use.

The leads 1 and 2 extend to a substation and incoming connections for this'station-are completed from a connector over the leads 8, 4 and 5. The combined line and cut off relay 6 is arranged to operate in two stages according as to whether it is energized over its top or bottom winding.

Suppose now that the subscriber under consideration initiates a call. Then he removes his receiver, a circuit is completed as follows: battery, both windings of common start relay 7, lower wlnding of line relay 6 of the calling line, back contact and armature 11, conductor 1, subscribers loop, conductor 2, armature 12 and its back contact,-

6 then receives enough current for it to operate its armature 10 only, whereby the callmg line is placed 1n conchtion to be found by the finder-switch allott-er. The operation of armature 8 also completes acircuit for relay 13, which thereupon energizes and applies earth at armature 14: to the test contact-s associated with all the lines in the group: except those actually in use. Moreover, at armature 9 relay 7 completes a circuit as tollows earth,

tact 17 in the bank of the allotter FA, homing wiper 18, back contact and armature 15, winding of series relay 19,. interrupter contact and magnet 20 to battery. The wipers armature 9 and its front contact, normal conof the finder allotters are thus advanced one step before the above circuit is opened at armature 15. The control of the hunting operation is then transferred to the test wiper 21 and this operation continues until wiper 22 to which earth is not connected. At arm-atur-e 16 a circuit-is prepared for line relay 23 of the allotter, this circuit not being operative for the present owing to: the fact that ,l l5 21 engages a contact, for instance the contact it is open at armature 2d of series relay 19 L as long asthe allotter is hunting to. find an idle finder. l

Assuming that. the finder FS is the one taken into use, relay l9 de-energizres when.

the allotter'FA comes to rest and completes a circuitfor relay23 which thereupon energizes and atgarmature 25 completes a circuit for switching relay 27 of the finder al.- lott er; and stepping magnet. 28 of the finder FS, in series, and at armature 26 connects test wiper 29 to the junction of relay 27 and magnet 28. Since all the lines of the roup except the calling line have earth connected to their test contacts, unless the wipers of F3 are already standing on this line relay 527 is short-circuited and magnet 28 is energized and de-energized to step the wipers round until the calling line is found. When this occurs, relay 27 is no longer short-circuited and energizes, thereby at its armature 30 cornpleting a circuit for connecting relay 31. Relay 31 upon energizing, at armatures 32 and 33 connects the speaking leads through, at armature 34; connects earth to test wiper 29 and at armature 35 prepares a locking circuit for itself. The connection of earth to wiper 29 completes a circuit for the upper winding of line relay 6 which thereupon energizes fully and at armatures 11 and 12 disconnects conductors 1 and 2 from its lower winding and earth respectively. The circuit of relay 7 is thereby opened and unless other calls have been initiated in the meantime, it commences to de-energize. Upon the operation of armature 35, the following circuit is completed: earth, armature 30 and its front contact, wiper 36 and the contact on which it is resting, front contact and armature 35, contact 22, wiper 21, front contact and armature 15, series relay 19, stepping magnet 20 to battery. The finder allotter FA is thus advanced one step and by the operation of series relay 19 the circuit of relay 23 is opened so that it tie-energizes and opens the circuit of relay 27. Unless any other calls are waiting attention relay 7 now de-energizes and opens the circuit of relay 13 which de-energizes also. A circuit for restoring the finder allotter to normal is then completed as follows: earthed multiple contacts 36, wiper 18, back contact and armature 15, relay 19, magnet 20 to battery. Since this circuit is completed intermittently under the control of the interrupter contact until wiper 18 engages contact 17 which is now dead, the switch is restored to normal in readiness to complete other connections.

During the conversation the relays 6 and 31 are held up by earth fed back on release trunk conductor 37 from one of the numerical switches. When the calling party hangs up his receiver this earth is removed and relays 6 and 31 de-energize and the link is freed. It may then be used to establish a connection by way of the finder FS since when earth is removed from conductor 37, FS will no longer test busy in the bank of the finder allotter FA.

One important feature of the arrangement shown should be noted, namely that the finder allotter is stepped on after the calling line has been found irrespective of whether earth is fed back from the numerical switch. In the ordinary course, this earth will be sent back before the earth at armature 30 has been removed, but in case the trunk associated with the selected finder should be faulty, earth will not come back and relay 31 will de-energize. The removal of earth from test wiper 29 partially de-energizes relay 6, so that the circuit of relay 7 is again completed and since it i slow it will not have released durin this interval. Hence the finder allotter Fr will again hunt for an idle finder, and this will then operate to find the calling line and the connection will be completed thereover.

The operation when a connection is extended from the group served by the finders such as FS is precisely similar and it will be seen that as soon as the link has been taken into use by either FA or FA, it is impossible for it to be seized over the other path. Moreover it is not possible for more than one connecting relay to be operated at once since the initial energizing circuit is completed from the finder alotter.

Fig. 3 depicts the bank wiring of the finder allotters FA and FA, only the banks engaged by the wipers 18 and 21 being shown. Tl e sv-ritches are shown as having 25 points and a total of 18 trunks are provided of which 7 are individual to each switch and the remaining four are common. Since the number available to each switch is only 11, they are multipled twice round the bank so as to avoid the nece :ity of an excessive movement on returning to normal, there being thus two nor mal positions. The lead 38 in Fig. 3 extends to the contact such as 9 of the common start relay.

Thus by means of the invention one of the most serious disadvantages of small capacity finder switches has been overcome. It will be understood. however, that the invention is equally applicable to large capacity finders though, as pointed out above, the greatest advantages of the arrangement are to be found in connection with finders of small capacity. v

\Vhat is claimed is:

1. In a trunking system of a telephone system, a group of line finder switches divided into sub-groups, subscriber controlled numerical switches for extending connections, a certain number of said last switches being allotted individual y to a corresponding number of finder switches comprising one subgroup, a nd another number of said switches each of which is connected in common relation with a plurality of finder switches of another sub-group.

2. In a trunking system of a telephone system, a group of line finder switches divided into sub-groups, subscriber controlled numerical switches for extending connections, a certain number of said lastswitches being allotted individually to a corresponding number of finder switches comprising one subgroup, another number of said switches each (it which is connected with a plurality of finder switches of another subgroup, and a third number of said switches each of which is connected in common relation with a greater plurality of finder switches of a third sub-group than in the second.

3. In a trunking system of a telephone system, a group of line finder switches divided into sub-groups, subscriber controlled -numerical switches for extending connections, a certain number of said last switches being allotted individually to a corresponding number of finder switches comprising one sub group, another number of said switches each of which is connected with a plurality of finder switches of another sub-group, and means for causing-the said numerical switches to be allotted for use by calling lines in a definite order of priority in which order the switches are accessible from successively larger groups of subscribers lines.

4. In a trunking system of a telephone system, a group of line fiuder switches divided into sub-groups, subscriber controlled numerical switches for extending connections, a certain number of said last switches being allotted individually to a corresponding number of finder switches comprising one subgroup, another number of said switches each of which is connected with a plurality of finder switches of another sub-group, and means for causing the finder switches and the numerical switches to be used in a definite rder of priority.

5. In a telephone system, finder switches for connecting a calling subscribers line to one of a group of first numerical switches, means for causing the finders to be taken for use in a definite order of priority, the finders first taken for use being linked to numerical switches individual to them while a number oi those taken into use thereafter are connected in common to another numerical switch. I

6. In a telephone system, groups of subscribers lines, some of said groups being larger than others of said groups, numerical switches, backwardly hunting switches for connecting subscribers lines to said numeral switches, and means for causing said numeral switches to be taken for use in a definite order of priority, in which order some of said numeral switches are accessible from successively larger groups of subscribers lines than other of said numerical switches.

7. In a telephone system, finder switches arranged in groups, a group of other switches, means for connecting certain of said finder switches to individual ones of said other switches, and means for connecting others of said finders in multiple to the other switches.

8. In a telephone system, a calling line, a plurality of. finder switches having access to said line, other finder switches, a plurality of numerical switches for extending connections' to called lines, certain of said numerical switches being individual to certain of the finder switches while others are directly connected without intervening switches to a number of the finder switches, and means for causing the first of the numerical switches to be taken for use ahead of those which are common to a number of the finders.

-9. In a telephone system employing baclc wardly hunting switches for connecting subscribers lines to numerical switches, means including an allotting switch for causing the numerical switches to be taken into use in a definite order of priority, and means for caus ing the said allotter to be moved to a dis tinctive position at any time no finder under its control is performing a hunting operation.

10. In a telephone system, numerical switches for extending connections, backwardly hunting switches for connecting the numerical switches to subscribers lines, means including an allotting switch for causing the finders and numerical switches to be taken into use in a definite order of priority, and finder controlled means for completing a circuit for advancing the allotter responsive to the finders coming to rest on a calling line. 7

11. In a telephone system, groups of calling lines, a corresponding number of groups of trunks, means for enabling the lines of one group to extend connections only via a particular group of trunks and for enabling the lines of more than one group to extend connections via a trunk of another of said groups.

12. In a telephone system, a calling line equipped with a combined line and cut off relay, a finder switch having access to said line, a second relay, a circuit including said first and second relays completed responsive to the initiation of a call for operating said second relay, means operated by said second relay for partially operating said first relay to thereby distinguish the calling line from others to which the finders have access, and said second relay at the same time causing the first relay to become fully operated by causing a preselected finder to find the calling line.

13. In a telephone system, groups of subscribers lines of various sizes, numerical switches, and means for causing said numerical switches to be taken for use in a definite order of priority, in which order some of said switches are accessible from successively larger groups of subscribers lines than other of said switches.

14. The method of maintaining a 1 prescribed order of use of the finder switches of a graded multiple finder system which consists: of connecting the finders to the banks of a homing type distributor in said prescribed order; of starting said distributor from its home position responsive to the initiation of a call in search of the first idle finder connected to its banks; and of return ing said distributor to its home position immediately after a finder has been operated into connection with a calling line.

15. In a telephone system, a group of lines, a group of finders having access to said lines, a distributor switch having a normal position, means responsive to simultaneous calls initiated by a plurality of said lines for start ing said distributor to select a finder to oper ate it into connection with one of said calling lines and for rcoperating said distributor to select and operate another finder switch into connection with another one of said calling lines, and means responsive to the establishment of a connection with the last of said calling lines for returning said distributor to its normal position.

16. In a telephone system, a group of lines, a group of finder switches having access to said lines, a distributor switch having a normal position, means responsive to the initiation of a call on one of said lines for operating said distributor out of its normal position to select and operate a finder into connection with said calling line, and means responsive to the establishment of said connection for returning said distributor to its normal position.

17. In a telephone system, a group of lines, a group of finder switches having access to said lines, a distributor switch having a normal position, a start relay energized responsive to the initiation of a call on one of said lines and deenergized when a finder connects with that line, means responsive to the energization of said start relay for operating said distributor out of its normal position to select and operate a finder into connection with the calling line, and means controlled by the deenergization of said start relay for returning said distributor to its normal position.

18. In a telephone system in which a homing type distributor is started from normal responsive to the initiation of a call on a line to select and control a finder, to find that line and then release from the finder, a return to normal circuit and a finder selecting circuit in said distributor, a relay energized upon the initiation of a call to open said former and to close said latter circuit, a trunk line outgoing from said finder, a relay in the finder operated when the calling line is found to connect that line to said trunk, means responsive to a successful operation of said finder relay for restoring said first relay and responsive to an unsuccessful operation of said finder relay for maintaining said first relay energized, and means in said distributor operated over said finder selecting circuit after said finder relay has been operated for selecting another finder for operating it into connection with said calling line.

19. In a telephone system, a subscribers line, a plurality of finders having access to said lines, trunks outgoing from said finders. a distributor having a normal position, a return to normal circuit in said distributor, means responsive to the initiation of a call on one of said lines for opening said return to normal circuit and for starting said distributor out of its normal position in search or an idle finder, means in said distributor responsive to the finding of an idle finder for seizing and starting that finder in search of said calling line, means in said finder for establishing a connection between said line and trunk, means in said distributor responsive to the finder finding said line for operat ing said finder connecting means and for disassociating said distributor from said finder and for closing said return to normal circuit to return said distributor to normal.

20. In a telephone system, subscribers lines divided into a plurality of groups, finder switches having access to said lines, said finders being arranged in groups corresponding to said line groups, a plurality of trunks outgoing t'roin said finders, direct connections between said finders and trunks, the sum of the numbers oi trunks available to said individual line groups is greater than the number of said outgoing trunks.

21. In a finder switch system in which some finder switches are assigned to the individual use of a group of lines and other finders as signed to difi'erent groups oi lines are connected in multiple with each other, a finder allotter, means responsive to the initiation of a call by one of said lines for starting saif allotter in search of an idle finder, and means for causing said allotter to select a finder assigned to the individual use of the line group containing the calling line it such a finder is idle.

22. In a telephone system in which a homing type distributor is started from normal responsive to the initiation of a call on a line to select and control a finder to find that line and then release from the finder, a return to normal circuit and a finder selector circuit in said distributor, and a relay energized upon the initiation of a call to open said former and to close said latter circuit.

In witness whereof, I hereunto subscribe my name this 28th day of April, 1925.

W'ILLIAM AITKEN. 

